Both according to the owners manual, unless I get under there and find someone swapped in a LSD.
Oh, steering box too.
For the transmission I would use the redline synthetic 75W 90ns, you would see a huge difference in shifting gears.
For the differential and steering box the Shell spirax HD will work fine.
'75 Giulia Nuova Super 1300 Blu Olandese
'71 Euro Berlina 2000 (on a restoration process)
'85 GTV6 Nero
'87 Milano Verde
'87 Milano Platinum